This invention relates to a novel cell culture system and more particularly to improved continuous cell culture filter apparatus and method which is useful in the large scale cultivation of mammalian cells.
The development of reactors and related apparatus for growing in culture large quantities of the fragile, complex cells that synthesize commercially valuable proteins is of significant importance in recent years. Methods for such large scale growth of mammalian cells are well-known and are described, for example, in several articles by Tolbert et al., Biotech. Bioeng. XXIV, 1671-1679 (1982); Tolbert and Feder, Ann. Rept. Ferm. Proc., Vol. 6, Ch. 3, pp. 35-74 (1983); Harakas, Ibid., Vol. 7, Ch. 7, pp. 159-211 (1984); and references cited in said publications.
The use of a cell culture reactor with controlled agitation by means of a magnetic stirrer bar or a mechanically driven impeller on a shaft is a typical feature of suspension cell culture apparatus. Examples of such apparatus are described in U.S. Pat. Nos. 2,958,517; 3,039,932; 3,572,651; 3,622,122; and 3,649,465. These are essentially batch type spin culture devices or spinner flasks in which the cells are incubated in a fixed amount of nutrient under appropriate culture conditions until cell growth has ceased.
Continuous cell culture systems and apparatus also have been described heretofore in which fresh medium can be added and spent medium can be separated from the growing cells by filtration and withdrawn from the flask on a continuous or semi-continuous basis as seen from U.S. Pat. Nos. 4,166,768 and 4,178,209.
In order to provide a gentle agitation of the suspension cell culture system, apparatus has been developed with flexible sheets on the agitator arm which are adapted to flex and billow like a sail with the liquid flow during rotation of the agitator arm as disclosed in U.S. Pat. No. 4,289,854.
Notwithstanding the advantages of the aforesaid cell culture system with the flexible agitator sheets, difficulties have arisen with the assembly - disassembly capability of the apparatus. It is desired to alleviate these difficulties and to improve the apparatus for commercial use in the production of medically important proteins and hormones. Complete cleaning of the apparatus between various cell culture runs to satisfy Food and Drug Administration (FDA) validation would be facilitated by improved assembly - disassembly capability of the apparatus.